Method of filling a vessel completely with a liquid



METHOD OF FILLING A VESSEL COMPLETELY WITH A LIQUID Press.

Recorder Pres s are fransaucer- B. H'. VAN HORNE ETAL ,656

v Filed Dec. 4. i963 3U 49 we)? Pressure vessel Curve/ Curve 2 i CU/"V63 Curv4 Vo/ume- CC. I

, INVENTORS 5 ever/ey/i Van Abrne BY fl/aen M Hanson HTTOR/VEYS UnitedStates Patent 3 344 656 METHOD OF FILLINE; A VESSEL COMPLETELY WITH A LIQUID Beverley H. Van Horne and Alden W. Hanson, Midland,

Mich., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Filed Dec. 4, 1963, Ser. No. 327,943

4 Claims. (Cl. 73-37) This invention relates to amethod of filling a vessel completely with a liquid when the vessel has at least one unvented portion initially filled with a gas which is immiscible with or incompletely soluble in said liquid, and more particularly, to a method of eliminating trapped gas in unvented vessels on attempting to fill them completely with a liquid.

Vessels initially filled with a gas which is immiscible with or incompletely soluble in a liquid which is to completely fill the vessel cannot be completely filled with the filling liquid by ordinary methods because some of the initial gas may be trapped by an unvented portion of the vessel and the filling liquid. This may be seen by gas bubbles trapped along the internal surfaces of the vessel or by pockets of gas trapped in areas of the vessel which are not accessible to the filling liquid. The filling liquid is thus prevented from contacting all internal surfaces of the vessel. If the filling liquid is a cleaning agent, it follows that all internal surfaces of the vessel would not be in contact with said cleaning agent and thus would result in an incomplete cleaning performance.

In the area of hydrostatic testing of pressure vessels, wherein the pressure vessel to be tested is pressurized with a substantially non-compressible liquid While a recorder plots at the start of pressurization of said vessel the volume of liquid introduced or its equivalent against the resulting pressure generated in the pressure vessel, the plot of pressure versus volume should be of a constant slope until the yield point of the vessel is reached. It has been observed that this plot is not of a constant slope at the beginning of the test because of trapped, immiscible, insoluble gas, e.g., air, in the test vessel. As the vessel is pressurized, the gas is compressed into solution and the plot then becomes one of a curve of constant slope until the yield point is reached. The accuracy of this plot can be further improved if the initial part of the curve, which is non-linear and is called a foot, is eliminated so that the entire curve is linear until the yield point is reached. The method of this invention substantially eliminates this foot.

Accordingly, it is an object of the present invention to provide a method of eliminating the residual gas or the gas of a gas-occupied space in a vessel initially containing a gas which is trapped in unvented portions on attempting to completely fill the vessel with a liquid, so that the vessel may be filled completely with the liquid.

Another object of the present invention is to provide a method of completely filling a vessel with a liquid so that all internal surfaces of the vessel are in contact with the liquid.

A further object is to provide a method which provides an improvement in the hydrostatic testing of pressure vessels.

These and other objects and advantages will be apparent from reading the detailed description in connection with the accompanying drawings presented hereinafter.

FIGURE 1 is a block diagram of a nondestructive hydrostatic pressure testing assembly used to illustrate the method of the instant invention.

FIGURE 2 consists of four curves illustrating results of the method of the instant invention as applied to said testing assembly.

In general, the instant invention is comprised of a method for completely filling the free space in a vessel with a filling liquid, the vessel being initially filled with a gas which is not completely soluble in the filling liquid and the interior of said vessel having at least one unvented portion in which gas may be trapped by the liquid introduced into the vessel. The steps of the method include introducing into the vessel a fluid which is capable of either displacing the trapped gas or reacting with the trapped gas, said fluid being miscible with and soluble in said filling liquid on reacting with said gas to provide products soluble in and miscible with said filling liquid, and introducing the filling liquid into the so-treated vessel and substantially completely filling the vessel with the filling liquid.

The term fluid, as used herein, refers both to gaseous and liquid materials. However, ordinarily, gases are used in the instant method.

In carrying out the method of the instant invention, a pressure vessel, for example, initially filled with a gas, is purged with a purge gas which is capable of being sorbed in a liquid. The purge gas is introduced into said vessel through any convenient outlet in a continuous stream while allowing gas to escape from a convenient outlet until an analysis of the escaping gas by conventional means, for example an Orsat-ty-pe apparatus, no longer detects any of the gas initially present.

Liquid is then introduced into said vessel so filled with purge gas until all the purge gas is sorbed therein and the liquid completely fills the vesseLThe flow of liquid into the vessel is terminated at a point at which the internal pressure of the vessel just begins to rise with the continued addition of liquid into the vessel, as indicated by a pressure gauge suitably attached to said vessel.

The term pressure vessel, as used herein, means closed or scalable containers of any shape which ordinarily are subjected to pressure in use and is meant to include gas storage cylinders, reactor tanks, pressure tubing and pipes, tank cars, storage tanks, boilers, boiler tubes, missile parts and the like.

Tab-1e 1 which follows present-s illustrative purge gases, purge liquids and corresponding filling liquidswhich can be used in carrying out the method of the instant invention.

basic soln.; weak cadmium, lead or copper salt soln.; alkaline bleach soln.

Weak basic soln.; amines (e.g., ethanola-mine, diethanolamine, triethanol; amine).'

All halogen acids Nitric oxide.

Nitrogen oxide. Nitrous oxide.

Dinitrogen tetroxide. Oxygen Strong reducing agents; al-

kaline soln. of pyrogallic 'acid; hydroquinone; sulfur dioxide-I-water-ksodium hydroxide. Formic acid Ammonia+water. Chlorine. Bromine.

' 3 Table 1.-Cntinued Purge gases: Filling liquids Ammonia Water; weak acidic soln.; organic acids; boric acid; phosphoric acid; soln. of formaldehyde; salts of copper, silver, nickel (e.g., chlorides and sulfates). Methylamine. Methoxyamine. Fonmaldehyde Water. Methane Water; ethyl alcohol. Ethane Water; ethyl alcohol. Propane Ethyl alcohol; ether. Ethylene Water; ethyl alcohol. n-Butane Ethyl alcohol. Isobutane Water; ethyl alcohol. Propylene Water; ethyl alcohol. Acetylene Water; ethyl alcohol. Trirnethylamine Water; ethyl alcohol; disulfuric acid in water.

Purge liquids: Filling liquids Methanol Water. Ethanol Water. Isopropanol Water. n-Propanol Water. Methyl cellosolve Water. Cellosolve Water. 'n-Butyl cellosolve Water. Methyl carbitol Water. Carbitol Water.

Acetone Water.

Methyl cellosolve acetate Water.

1 Alkaline bleach soln.

2 Sulfur dloxlde+water; alkaline cyanide soln. (sodium cyanide in water bromine cyanide chlorine cyanide).

f Strong organic acids strong inorganic acids (hydrochloric acid, sulfuric acid, nitric acid, hydrogen sulfide),

To illustrate further the practice of the invention, air may be removed from a vessel by purging said vessel with carbon dioxide thus displacing the air from said vessel. The vessel can be substantially completely filled with water. The carbon dioxide gas dissolves in the water thus leaving the vessel completely filled with liquid.

Any combination of purge fluid and filling liquid may be used to practice the method of the instant invention so long as the purge fluid is completely sorbed in the filling liquid under the conditions occurring during the operation of this invention. For example, the purge gases that may be used in combination with a filling liquid such as water include but are not limited to carbon dioxide, hydrogen sulfide and sulfur dioxide, among others. Where the filling liquid is oil, purge gases including but not limited to carbon dioxide, nitrogen and the like may be used in practicing the method of this invention.

In practicing the invention wherein a liquid is used to purge the vessel free of the gas, e.g., air, initially therein, methanol, for example, can be used as the purge liquid and water the filling liquid.

Another embodiment of the inst-ant method comprises introducing a filling liquid into a vessel until substantially all of the initial gas is displaced therefrom. The space above the filling liquid is then purged with a fluid which is capable of sorption in said liquid. Filling liquid is then, once again, introduced into the vessel until the vessel is substantially completely filled with said liquid.

The invention, as heretofore described, may be further modified by adding one or more of the following steps:

After the gas initially filling the vessel is eliminated by the desired purge gas, a one way check valve connected to the outlet on the vessel is opened and at the same time, the filling liquid is introduced into the vessel so that most of the purge gas will be displaced by said filling liquid. The check valve is closed while continuing the admission of said filling liquid into said vessel until all the remaining purge gas is dissolved in the liquid and the liquid completely fills the vessel.

This step, if incorporated into the afore-mentioned variations, will reduce the time needed to achieve complete filling of the vessel.

Another step which may be used which modifies the method of this invention is to initially evacuate the vessel to eliminate much of the initial gas in the vessel.

Wetting agents such as soaps, surfactants based on alkylaryl polyether alcohols, sulfonates, sulfates and the like may be added to the filling liquid, for example, in amounts ranging from less than 0.001 to about 0.01 or more weight percent (depending on the agent) based on the weight of liquid introduced into the vessel, to insure complete filling of the vessel. If the purge gas is acidic, then basic wetting agents may be employed and vice versa.

This invention has particular utility in hydrostatic pressure testing of pressure vessels such as steam generators, reaction vessels, pipe lines as for transporting petroleum and natual gas and the like, wherein the vessel preferably is to be completely filled with a liquid, usually oil or water, and then pressurized with more of the liquid while observing the volume of liquid so used and the corresponding pressure rise in the vessel. In making hydrostatic pressure tests of this kind, the presence of an immiscible gas, usually air, which may be trapped in the vessel on initial filling with the liquid, mitigates against obtaining an accurate correspondence between the volume of pressurizing liquid injected into the filled vessel and the resulting pressure rise. By practicing the method of the instant invention, any such trapped immiscible gas may be eliminated prior to pressure testing. The invention is also useful in those instances where a vessel is to be completely filled, as when using cleaning solvents to clean the interior surfaces as, for example, in descaling steam generators by filling the interior with dilute, inhibited hydrochloric acid.

The method of this invention may also be used in the cleaning of bubble cap towers and, in particular, in the cleaning of the bubble caps.

The vessel in which the instant invention is to be carried out may be constructed of conventional materials such as iron, stainless steel, glass, aluminum and the like.

If an iron vessel is used, care must be taken so as not to use acidic gases or acidic solutions in carrying out the method of the instant invention. Thus, weak basic solutions may be used alone or in combination with an acidic gas so that a complete neutralization reaction results therefrom.

Use of glass vessels prohibits the use of hydrogen fluoride as a purge gas or filling liquid and strong caustic solution as a filling liquid.

Use of aluminum vessels requires that no strong caustic (NaOH) or inorganic basic solutions be used as the filling liquid. Amines, inorganic bases, weak acidic solutions and neutral solutions can be satisfactorily employed as filling liquids and hydrogen sulfide, ammonia, carbon dioxide and the like as purge gases in this case.

The following example is illustrative of the invention but is not meant to limit it thereto.

Example In order to illustrate the effect of the method of the instant invention on the hydrostatic testing of pressure vessels, a hydrostatic pressure testing assembly was prepared as shown schematically in FIGURE 1. This assembly utilized a poitive displacement piston-type delivery pump. The pump was connected to a fluid supply source, namely, water, which in turn was coupled to a cylindrical vessel 6 inches in diameter and 26 inches in length. A strain gauge pressure transducer also was attached to the test vessel. The transducer was in turn coupled through an amplifier to a Houston X-Y recorder.

Water was continually pumped into the vessel thereby pressurizing said vessel. A plot of pressure in p.s.i.g. in the vessel versus volume of water introduced into the vessel after the vessel was supposedly filled with water was recorded as seen in curve 1 of FIGURE 2. Ordinarily, if the vessel was completely filled with water at the start of the pumping of additional Water into the vessel and the recording, a curve having a constant slope, until the yield point of the vessel was reached, would be recorded. However, as seen in curve 1 of FIGURE 2, the curve varies in slope up to about 100 p.s.i.g. and 11.5 cc. water injection after start of the pressure test even though the yield point of the vessel is about 1800 p.s.i. At this point, all gases which remained in the vessel at the start of the recording, when it was supposedly filled with water, were absorbed in the water due to the increasing pressure on said gases. Once these gases were so absorbed, the curve becomes one of constant slope Within the elastic deformation range of the vessel as increasing amounts of water are pumped into the vessel.

In applying the method of the instant invention to this process, the above vessel was evacuated to a maximum of about 2 mm. Hg, flushed with CO evacuated to about 2 mm. Hg once more and then filled with water as previously described. Curve 2 of FIGURE 2 illustrates the substantially complete filling of the vessel with water. After the vessel was supposedly filled with water, and the recording was started, it took only about an additional 6 cc. of water before the slope of the curve became constant as opposed to over 11 cc. of water when not using the method of this invention.

In another experiment, said vessel was purged with CO thus displacing the air from said vessel. Water containing 100 cc. of N NaOH was introduced into the vessel. The empty space between the top of the vessel and the surface of the water-NaOH solution was evacuted. The NaOH reacted with all CO remaining to produce small quantities of Na CO which were dissolved in the solution. Water was then introduced into the vessel thereby pressurizing said vessel. Curve 3 of FIGURE 2 shows that it took only about an additional 5 cc. of water before the slope of the curve became constant.

These tests illustrate that the method of the instant invention allows one to till a vessel substantially with a liquid thus improving existing methods for hydrostatic testing of pressure vessels and vessel cleaning techniques.

When the filling liquid itself was completely degassed prior to being introduced into the vessel and/or one of the aforementioned wetting agents was added to the filling liquid prior to being introduced into the vessel, again using the carbon dioxide purge fluid, the curve was one of constant slope even at the beginning of the test without any foot whatsoever being present. This is seen in curve 4 of FIGURE -2.

In a manner similar to the foregoing, a vessel can be completely filled with a liquid using other purge gases or purge liquids listed in the aforementioned table.

Various modifications can be made in the method of the present invention without departing from the spirit or scope thereof, for it is understood that we limit ourselves only as defined in the appended claims.

What is claimed is:

1. The method of completely filling the free space in a vessel with -a liquid, the vessel being initially filled with a gas which is immiscible with and insoluble in said liquid, the interior of said vessel having at least one unvented portion in which said gas will be trapped by the liquid on being introduced into the vessel, which comprises:

(a) purging the vessel with a fluid which is capable of sorption in the liquid; and

(b) introducing the filling liquid along with a wetting agent into the vessel until all the remaining gases are sorbed by said liquid and the liquid substantially completely fills the vessel.

2. A method in accordance with claim 1 wherein the vessel is evacuated before it is purged with the purge fluid.

3. In a process for the non-destructive hydrostatic testing of pressure vessels, wherein the pressure vessel to be tested is pressurized with a substantially non-compressible liquid which a recorder plots at the start of pressurization of said vessel the equivalent volume of liquid introduced against the resulting pressure generated in the pressure vessel, the improvement which comprises:

(a) evacuating the vessel to be tested;

(b) purging the vessel to be tested with a fluid which is capable of sorption in the test liquid prior to introducing test liquid; and

(c) introducing said test liquid into the vessel until all the fluid is sorbed in said liquid and the liquid substantially completely fills the vessel.

4. The method in accordance with claim 3 wherein the purge fluid is a gas.

References Cited UNITED STATES PATENTS 1,591,932 6/1926 Young 141-8 2,539,843 1/195'1 Kerr 73 37 2,810,776 10/1957 Brill 1415 OTHER REFERENCES Smiths College Chemistry, sixth edition, ed. by Ehrit Appleton-Century Co., Inc., N.Y. 946p. 348 relied upon. Copy 430'.

LOUIS R. PRINCE, Primary Examiner. S. C. SWISHER, Assistant Examiner. 

1. THE METHOD OF COMPLETELY FILLING THE FREE SPACE IN A VESSEL WITH A LIQUID, THE VESSEL BEING INITIALLY FILLED WITH A GAS WHICH IS IMMISCIBLE WITH AND INSOLUBLE IN SAID LIQUID, THE INTERIOR OF SAID VESSEL HAVING AT LEAST ONE UNVENTED PORTION IN WHICH SAID GAS WILL BE TRAPPED BY THE LIQUID ON BEING INTRODUCED INTO THE VESSEL, WHICH COMPRISES: (A) PURGING THE VESSEL WITH A FLUID WHICH IS CAPABLE OF SORPTION IN THE LIQUID; AND (B) INTRODUCING THE FILLING LIQUID ALONG WITH A WETTING AGENT INTO THE VESSEL UNTIL ALL THE REMAINING GASES ARE SORBED BY SAID LIQUID AND THE LIQUID SUBSTANTIALLY COMPLETELY FILLS THE VESSEL. 